The major goal of this project is to determine the extent to which changes in plasma levels of specific lipoproteins, lipoprotein subspecies, and apolipoproteins are associated with quantitative changes in coronary atherosclerosis during the course of a controlled four-year risk factor intervention program. The study groups consists of 300 patients admitted to Stanford University Medical Center for management of coronary artery disease (transluminal percutaneous coronary angioplasty, coronary artery bypass surgery, or medical treatment). Coronary angiography and computerized quantitation of non-bypassed or non-dilated coronary artery segments have been carried out at baseline on all subjects and will be repeated at four years following medical management (all subjects) and intensive multiple risk factor is being carried out under separate funding at Stanford. The special intervention program at Stanford includes improved nutrition, weight reduction, increased aerobic exercise, stress management, and individualized treatment including pharmacologic reduction of low density lipoprotein cholesterol, elimination of cigarette use, and reduction of hypertension. Initial lipoprotein analyses on all 300 subjects were performed one to three weeks after medical stabilization, or six weeks after surgery, and are being repeated annually during four year of follow-up. In addition, pre-treatment samples will be obtained on al subjects beginning HMG CoA reductase-inhibitor treatment. Subfractions of plasma very low density (VLDL), intermediate density lipoprotein (IDL), low density (LDL), and computer-based quantitation procedure. LDL and HDL subspecies are also measured by AII and B in plasma, and apo B in LDL are measured by immunoassay. Analysis of lipid make it possible to identify those lipoprotein parameters most closely involved in the disease process. The results will also indicate whether detailed measurements of specific lipoprotein subclasses and apolipoproteins are more informative that conventional lipid measurements in predicting changes in coronary artery disease and in assessing the effects of strategies directed at its prevention and treatment.